I'm not sure where you're reading your reviews, or maybe I just didn't notice which events are ignored, but the main subplot for IM3 was Tony dealing with the PTSD he developed in New York after those events, and it was in no way subtle about it.
I can give no specifics on what might have been ignored because the reviews I read didn't give any either. All of them were on IMDb I think. Since that "flaw" was mentioned in 5 or 6 out of the maybe 12-15 I read I thought it might have some truth to it. But even better if it was just BS.